1. Field of the Invention
This invention concerns lubricating compositions having improved oxidation stability due to the presence of an alkylamine substituted benzotriazole.
2. Description of Related Art
Oxidation stability is an important requirement for all lubricants, including automotive lubricating oils, industrial oils, and greases. The major cause of oxidative instability is the auto-oxidative breakdown of hydrocarbons in the lubricants and the concomitant formation of acids and other undesirable oxygenated species, including sludge. Auto-oxidative breakdown is strongly catalyzed by traces of metal ions (especially copper and iron) which become solubilized when the lubricant contacts a metal surface. One way to control auto-oxidation is to add one or more metal deactivators to the lubricant. In general, these deactivators prevent such undesirable catalytic reactions from occurring in two different ways: The metal deactivators form impervious films on the metal surface, thereby preventing dissolution of the metal ions (these are called "film forming metal passivators"), or the metal deactivators form complexes with solublized metal ions, thus rendering them inactive as catalysts (these are called "soluble metal deactivators").
Certain benzotriazole derivatives are known metal deactivators of the film forming type. For example, U.S. Pat. No. 3,697,427 discloses the use of benzotriazole and certain alkyl benzotriazoles (e.g. methylene bis-benzotriazole) in synthetic lubricating compositions.
Similarly, U.S. Pat. No. 3,790,481 discloses a polyester lubricating base stock that contains, among other additives, a copper passivator selected from methylene bis benzotriazole, benzotriazole, alkyl benzotriazoles, and naphthotriazole.
U.K. Patent 1,514,359 discloses the use of certain bis-benzotriazoles in functional fluids wherein the benzotriazole moieties are connected by alkylene and cycloalkylene groups, carbonyl groups, a sulphonyl group, oxygen, or sulfur atoms. The benzotriazole moieties also have dialkylamino methyl groups attached.
U.K. Patent 1,061,904 discloses the use of certain substituted benzoimidazoles and benzotriazoles as metal deactivators in lubricating compositions and functional fluids.
However, none of these patents (the disclosures all of which are incorporated herein by reference) disclose the particular alkylamine substituted benzotriazole containing lubricant compositions described hereafter.